1. Technical Field
This invention relates generally to underground fluid pumping and sampling systems and more particularly, to a system for installing such underground systems.
2. Discussion
Recent concerns over environmental quality have resulted in various government-imposed environmental regulations with regard to ground water quality and landsite cleanup projects. Among such regulations are requirements relating to the monitoring and sampling of ground water quality. In response to these requirements, water quality analytic capabilities have been improved and water sampling equipment has been developed. Much of the previously developed sampling equipment has not been effective, however, in obtaining consistent, non-contaminated water samples that are accurately representative of the water system from which the sample is taken.
The inadequacies of previous sampling equipment stem largely from causes such as cross-contamination between sampling sites, ineffective and inconsistent field cleaning methods, contamination due to equipment handling, and inconsistent well depth sampling. In addition, much of the previous equipment has proved to be complicated to operate, inordinately expensive, and impractical for sampling at remote locations where site access is severely limited.
A major component of the expense of ground water sampling is the cost and effort required to dig and install a well for insertion of the sampling apparatus. In response, devices have been developed which avoid the necessity of digging a well by having the device adapted to be driven directly into the ground. A serious problem with such devices, however, is their tendency to bring contaminants down from higher depths to the sampling depth. This can cause contamination of the sample at the desired depth. A ground water monitoring device which addressed this problem is described in U.S. Pat. No. 4,669,554, sold under the trademark HYDROPUNCH.TM. by Q.E.D. Environmental Systems, Inc., of Ann Arbor, Mich. That patent describes a ground water monitoring device which does not require drilling of a well, but instead includes a drive cone attached to its lower end so that the entire apparatus can be driven into the ground. Once the desired depth is reached, the pipe string used to drive the device is withdrawn slightly, thereby causing a portion of the device to slide upward with respect to the drive cone. This upward sliding motion opens an aperture and permits ground water to enter the device at the desired depth only, and not from any previous depths.
Devices such as the above-described U.S. Pat. No. 4,669,554 however, have some disadvantages. In general, these devices are relatively complex, costly and susceptible to damage. One reason is that such devices require sliding seals that open once the device reaches the desired depth. Such sliding seals are susceptible to sticking if they become dirty or damaged. For example, damage can occur while the device is being driven down, especially if hard objects are encountered during the descent. Once sliding seals become damaged or dirty, the seals stick, and the device may not open due to the increased drag on the seals. This happens because upward motion of the cone is resisted only by the friction of the dirt around it, and increased drag from a bent or dirty sliding seal will overcome the friction of the dirt, causing the cone to raise with rest of the apparatus. An additional problem with such devices is the necessity for replacing the entire system if a different diameter device is required. One further difficulty is that once the sample is taken and the device returned to the surface, the entire sampling apparatus must be emptied and cleaned before reuse for further sampling. Thus, it would be desirable to provide an underground sampling system which overcomes some or all of the aforementioned difficulties.
Accordingly, it is an object of the present invention to provide a simple and inexpensive system for installing an underground sampling apparatus without the necessity of drilling a well. It is a further object of the present invention to provide a system for ground water sampling which does not pull contaminants down to the sampling level.
It is an additional object of the present invention to provide a ground water sampling system which opens to receive a sample after reaching the desired depth, but which avoids the use of sliding seals. It is also an object of the present invention to provide such a system which is durable and not susceptible to damage.
It is a further object of the present invention to provide a system for delivering ground water sampling devices in which different diameter systems can be easily accommodated. It is still a further object of the present invention to provide a ground water sampling system in which multiple samples can be taken without requiring the entire system to be emptied and cleaned before reuse.